ABSORPTION OF ATMOSPHERIC NO2 BY PLANTS AND SOILS .1. QUANTITATIVE ESTIMATION OF ABSORBED NO2 IN PLANTS BY N-15 METHOD

Tomato, sunflower and com plants were grown in culture solution containing three different concentrations of 15N-Iabelled KNO3(260 ppm N, 105 ppm N, and 26 ppm N) as a nitrogen nutrient, and fumigated with 0.3 ppm NO2for 2 weeks during their vegetative stages. The amount of NO2nitrogen absorbed into the plants was estimated by “difference method” and “15N method.” “15N method” was found to give more probable values than “difference method.” According to “15N method,” the nitrogen derived from NO3was about 16% (tomato), 22% (sunflower), and 14% (com) of the increased amount of total nitrogen in the whole plants in the 105 ppm N plot, and these percentages increased in the 26 ppm N plot. Difference in nitrogen concentration of the culture solution resulted in big change in the dryweight increase of the tomato and sunflower plants, but the absorption rate of NO2nitrogen based on the dry weight changed slightly. The absorption rate of NO2nitrogen was around 0.8 mg (gDW)-1day-1in tomato and sunflower plants, and 0.3 mg (gDW)-1day-1in com plant. Leaves were found to be an active sink of NO2and the nitrogen of NO2seemed to be rapidly transformed into compounds of high molecules in the leaf cells. © 1979 Taylor & Francis Group, LLC.